Pollution (e.g., water pollution, noise, air pollution, etc.) has become a global issue as technology makes progress rapidly. Also, more people pay attention to pollution because people are aware of the importance of environmental protection. Further, many governments have given strict laws and enforced the same so as to effectively control pollution. For example, for decreasing air pollution toxic gas generated by fuel in a fuel tank is not allowed to discharge into the atmosphere as enacted by the governments.
However, air pollution caused by machines such as mowers, generators, pump motors, etc. is inevitable as known in the art. Note that the term “general machine” used in the present specification is referred to any of the above mowers, generators, pumps, etc.
Referring to FIG. 1, a typical general machine 10 comprises an engine 11, a fuel tank 12 provided above the engine 11, a fuel inlet 13 on a top of the fuel tank 12 in which fuel is flowed into the fuel tank 12 via the fuel inlet 13, and a cover 14 enclosed the fuel inlet 13 for preventing fuel from spilling out of the fuel inlet 13.
Moreover, the general machine 10 further comprises an air filter 15 provided besides the engine 11, a carburetor 16 for mixing fuel supplied from the fuel tank 12 with pure air supplied from the air filter 15 to make an explosive mixture which is then supplied to the engine 11 for combustion, and a crank case 17 having a crank shaft 18 adapted to rotate in response to the combustion. As an end, the purpose of developing mechanical power for starting motion in another machine is achieved by the general machine 10.
However, the prior general machine 10 suffered from a disadvantage. For example, as shown in FIG. 1 for facilitating fuel in the fuel tank 12 flowing into the carburetor 16 an air outlet 19 is provided on the top of the fuel tank 12. The provision of the air outlet 19 aims at utilizing atmospheric pressure to quickly direct fuel in the fuel tank 12 to the carburetor 16 so as to mix with pure air supplied from the air filter 15 for making an explosive mixture. Unfortunately, toxic gas may be generated by fuel in the fuel tank 12 to discharge into the atmosphere via the air outlet 19, resulting in air pollution. Thus, the need for improvement still exists.